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(#) Mismatched Log Tags

!!! ERROR: Mismatched Log Tags
   This is an error.

Id
:   `LogTagMismatch`
Summary
:   Mismatched Log Tags
Severity
:   Error
Category
:   Correctness
Platform
:   Android
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   1.1.0 (February 2015)
Affects
:   Kotlin and Java files
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/LogDetector.kt)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/LogDetectorTest.kt)

When guarding a `Log.v(tag, ...)` call with `Log.isLoggable(tag)`, the
tag passed to both calls should be the same. Similarly, the level passed
in to `Log.isLoggable` should typically match the type of `Log` call,
e.g. if checking level `Log.DEBUG`, the corresponding `Log` call should
be `Log.d`, not `Log.i`.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
src/LogExample.kt:9:Error: Mismatched tags: the d() and isLoggable()
calls typically should pass the same tag: TAG1 versus TAG2
[LogTagMismatch]
    Log.d(TAG2, "message") // warn: mismatched tags - TAG1 and TAG2
          ----
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`src/LogExample.kt`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers
import android.util.Log

const val TAG1 = "tag1"
const val TAG2 = "tag1"

class LogExample {
    fun test() {
        if (Log.isLoggable(TAG1, Log.DEBUG)) {
            Log.d(TAG2, "message") // warn: mismatched tags - TAG1 and TAG2
        }
    }
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/LogDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Using a suppression annotation like this on the enclosing
  element:

  ```kt
  // Kotlin
  @Suppress("LogTagMismatch")
  fun method() {
     d(...)
  }
  ```

  or

  ```java
  // Java
  @SuppressWarnings("LogTagMismatch")
  void method() {
     d(...);
  }
  ```

* Using a suppression comment like this on the line above:

  ```kt
  //noinspection LogTagMismatch
  problematicStatement()
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="LogTagMismatch" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'LogTagMismatch'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore LogTagMismatch ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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